Does that extra scholastic performance pay off latter in life? In my experience it does not.

But please don’t use this as an excuse! Slacking off will hurt you no matter what you think now.

Just put an effort comparable with your goal, then invest the free time you gained in more direct path.

Find yourself a mentor, read books, go to library and learn stuff that will pay off latter even if it does not come attached with scholastic bonuses.